ALTRUISM, EGOISM AND GROUP COHESION IN A LOCAL INTERACTION MODEL

In this paper we have introduced and parameterized the concept of ?group cohesion? in a model of local interaction with a population divided into groups. This allows us to control the level of ?isolation? of these groups: We thus analyze if the degree of group cohesion is relevant to achieve an efficient behaviour and which level would be the best one for this purpose. We are interested in situations where there is a trade off between efficiency and individual incentives. This trade off is stronger when the efficient strategy or norm is strictly dominated, as in the Prisoner?s Dilemma or in some cases of Altruism. In our model we have considered that agents could choose to be Altruist of Egoist, in fact, they behave as in Eshel, Samuelson and Shaked (1998) model.